Improvements in recombinant DNA technology have produced dramatic changes to the agricultural industry, in particular the approaches taken to improve crop productivity. A major concern is the effect of plant pests, such as plant parasitic nematodes, on productivity. Generally, plant parasitic nematodes invade a wide range of food, fibre and ornamental plants, causing damage to different plant tissues with varying severity on productivity. Parasitic nematodes cost the agriculture and horticulture industries approximately U.S. $78 billion per annum.
Plant parasitic nematodes are broadly classified as either migratory ectoparasites, sedentary ectoparasites, migratory ectoendoparasites, migratory endoparasites, or sedentary endoparasites, on the basis of their feeding patterns. Most crop damage is caused by sedentary endoparasites, for example the cyst nematodes heterodera sp. and Globodera sp. and the root knot nematodes meloidogyne sp., through their devastating effect on root structures. Juvenile nematodes invade the plant root and migrate to the vascular tissue where they induce a multinucleate feeding structure or syncitium from which the nematode feeds.
The most cost-effective and sustainable method for control of plant pests is the development of resistant plants. However, the development of this method of control in relation to parasitic nematodes has faced many difficulties. For example, bioassays for nematodes, such as the cereal cyst nematode, are long and labour intensive. Although natural resistance to plant parasitic nematodes occures in certain plant genotypes, the molecular basis of resistance was hitherto unknown. In particular, the molecular characteristics of a gene encoding a polypeptide which confers nematode resistance on a plant, has not been a straightforward procedure. Furthermore, until the present invention, even the chromosomal localisation of nematode resistance genes and genetic markers for nematode resistance, were unknown.